fix truncate when NS is set
Also: fix test to catch the issue
This commit is contained in:
Dhia Ayachi
Daniel Nephin
parent
5ae7c6a490
commit
079decdabd
36
agent/dns.go
36
agent/dns.go
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@ -1072,7 +1072,7 @@ func dnsBinaryTruncate(resp *dns.Msg, maxSize int, index map[string]dns.RR, hasE
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// trimTCPResponse limit the MaximumSize of messages to 64k as it is the limit
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// of DNS responses
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func (d *DNSServer) trimTCPResponse(req, resp *dns.Msg) (trimmed bool) {
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func trimTCPResponse(req, resp *dns.Msg) (trimmed bool) {
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hasExtra := len(resp.Extra) > 0
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// There is some overhead, 65535 does not work
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maxSize := 65523 // 64k - 12 bytes DNS raw overhead
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@ -1080,8 +1080,6 @@ func (d *DNSServer) trimTCPResponse(req, resp *dns.Msg) (trimmed bool) {
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// We avoid some function calls and allocations by only handling the
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// extra data when necessary.
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var index map[string]dns.RR
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originalSize := resp.Len()
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originalNumRecords := len(resp.Answer)
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// It is not possible to return more than 4k records even with compression
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// Since we are performing binary search it is not a big deal, but it
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@ -1103,6 +1101,10 @@ func (d *DNSServer) trimTCPResponse(req, resp *dns.Msg) (trimmed bool) {
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// This enforces the given limit on 64k, the max limit for DNS messages
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for len(resp.Answer) > 1 && resp.Len() > maxSize {
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truncated = true
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// first try to remove the NS section may be it will truncate enough
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if len(resp.Ns) != 0 {
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resp.Ns = []dns.RR{}
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}
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// More than 100 bytes, find with a binary search
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if resp.Len()-maxSize > 100 {
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bestIndex := dnsBinaryTruncate(resp, maxSize, index, hasExtra)
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@ -1114,13 +1116,7 @@ func (d *DNSServer) trimTCPResponse(req, resp *dns.Msg) (trimmed bool) {
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syncExtra(index, resp)
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}
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}
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if truncated {
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d.logger.Debug("TCP answer to question too large, truncated",
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"question", req.Question,
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"records", fmt.Sprintf("%d/%d", len(resp.Answer), originalNumRecords),
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"size", fmt.Sprintf("%d/%d", resp.Len(), originalSize),
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)
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}
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return truncated
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}
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@ -1169,6 +1165,10 @@ func trimUDPResponse(req, resp *dns.Msg, udpAnswerLimit int) (trimmed bool) {
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// Even when size is too big for one single record, try to send it anyway
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// (useful for 512 bytes messages)
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for len(resp.Answer) > 1 && resp.Len() > maxSize-7 {
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// first try to remove the NS section may be it will truncate enough
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if len(resp.Ns) != 0 {
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resp.Ns = []dns.RR{}
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}
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// More than 100 bytes, find with a binary search
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if resp.Len()-maxSize > 100 {
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bestIndex := dnsBinaryTruncate(resp, maxSize, index, hasExtra)
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@ -1189,14 +1189,24 @@ func trimUDPResponse(req, resp *dns.Msg, udpAnswerLimit int) (trimmed bool) {
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// trimDNSResponse will trim the response for UDP and TCP
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func (d *DNSServer) trimDNSResponse(cfg *dnsConfig, network string, req, resp *dns.Msg) {
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var trimmed bool
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originalSize := resp.Len()
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originalNumRecords := len(resp.Answer)
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if network != "tcp" {
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trimmed = trimUDPResponse(req, resp, cfg.UDPAnswerLimit)
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} else {
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trimmed = d.trimTCPResponse(req, resp)
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trimmed = trimTCPResponse(req, resp)
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}
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// Flag that there are more records to return in the UDP response
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if trimmed && cfg.EnableTruncate {
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resp.Truncated = true
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if trimmed {
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if cfg.EnableTruncate {
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resp.Truncated = true
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}
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d.logger.Debug("DNS response too large, truncated",
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"protocol", network,
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"question", req.Question,
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"records", fmt.Sprintf("%d/%d", len(resp.Answer), originalNumRecords),
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"size", fmt.Sprintf("%d/%d", resp.Len(), originalSize),
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)
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}
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}
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@ -4428,6 +4428,7 @@ func TestBinarySearch(t *testing.T) {
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msgSrc.SetQuestion("redis.service.consul.", dns.TypeSRV)
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msg.Answer = msgSrc.Answer
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msg.Extra = msgSrc.Extra
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msg.Ns = msgSrc.Ns
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index := make(map[string]dns.RR, len(msg.Extra))
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indexRRs(msg.Extra, index)
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blen := dnsBinaryTruncate(msg, maxSize, index, true)
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@ -6888,6 +6889,103 @@ func TestDNS_trimUDPResponse_TrimLimit(t *testing.T) {
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}
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}
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func TestDNS_trimUDPResponse_TrimLimitWithNS(t *testing.T) {
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t.Parallel()
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cfg := loadRuntimeConfig(t, `node_name = "test" data_dir = "a" bind_addr = "127.0.0.1" node_name = "dummy"`)
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req, resp, expected := &dns.Msg{}, &dns.Msg{}, &dns.Msg{}
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for i := 0; i < cfg.DNSUDPAnswerLimit+1; i++ {
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target := fmt.Sprintf("ip-10-0-1-%d.node.dc1.consul.", 185+i)
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srv := &dns.SRV{
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Hdr: dns.RR_Header{
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Name: "redis-cache-redis.service.consul.",
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Rrtype: dns.TypeSRV,
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Class: dns.ClassINET,
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},
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Target: target,
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}
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a := &dns.A{
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Hdr: dns.RR_Header{
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Name: target,
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Rrtype: dns.TypeA,
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Class: dns.ClassINET,
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},
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A: net.ParseIP(fmt.Sprintf("10.0.1.%d", 185+i)),
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}
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ns := &dns.SOA{
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Hdr: dns.RR_Header{
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Name: target,
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Rrtype: dns.TypeSOA,
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Class: dns.ClassINET,
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},
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Ns: fmt.Sprintf("soa-%d", i),
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}
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resp.Answer = append(resp.Answer, srv)
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resp.Extra = append(resp.Extra, a)
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resp.Ns = append(resp.Ns, ns)
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if i < cfg.DNSUDPAnswerLimit {
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expected.Answer = append(expected.Answer, srv)
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expected.Extra = append(expected.Extra, a)
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}
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}
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if trimmed := trimUDPResponse(req, resp, cfg.DNSUDPAnswerLimit); !trimmed {
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t.Fatalf("Bad %#v", *resp)
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}
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require.LessOrEqual(t, resp.Len(), defaultMaxUDPSize)
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require.Len(t, resp.Ns, 0)
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}
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func TestDNS_trimTCPResponse_TrimLimitWithNS(t *testing.T) {
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t.Parallel()
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cfg := loadRuntimeConfig(t, `node_name = "test" data_dir = "a" bind_addr = "127.0.0.1" node_name = "dummy"`)
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req, resp, expected := &dns.Msg{}, &dns.Msg{}, &dns.Msg{}
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for i := 0; i < 5000; i++ {
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target := fmt.Sprintf("ip-10-0-1-%d.node.dc1.consul.", 185+i)
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srv := &dns.SRV{
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Hdr: dns.RR_Header{
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Name: "redis-cache-redis.service.consul.",
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Rrtype: dns.TypeSRV,
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Class: dns.ClassINET,
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},
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Target: target,
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}
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a := &dns.A{
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Hdr: dns.RR_Header{
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Name: target,
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Rrtype: dns.TypeA,
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Class: dns.ClassINET,
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},
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A: net.ParseIP(fmt.Sprintf("10.0.1.%d", 185+i)),
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}
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ns := &dns.SOA{
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Hdr: dns.RR_Header{
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Name: target,
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Rrtype: dns.TypeSOA,
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Class: dns.ClassINET,
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},
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Ns: fmt.Sprintf("soa-%d", i),
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}
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resp.Answer = append(resp.Answer, srv)
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resp.Extra = append(resp.Extra, a)
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resp.Ns = append(resp.Ns, ns)
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if i < cfg.DNSUDPAnswerLimit {
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expected.Answer = append(expected.Answer, srv)
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expected.Extra = append(expected.Extra, a)
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}
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}
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req.Question = append(req.Question, dns.Question{Qtype: dns.TypeSRV})
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if trimmed := trimTCPResponse(req, resp); !trimmed {
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t.Fatalf("Bad %#v", *resp)
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}
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require.LessOrEqual(t, resp.Len(), 65523)
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require.Len(t, resp.Ns, 0)
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}
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func loadRuntimeConfig(t *testing.T, hcl string) *config.RuntimeConfig {
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t.Helper()
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result, err := config.Load(config.LoadOpts{HCL: []string{hcl}})
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